Gun turret power control



July 15, 1945 G. w. PoNTlUs, 3D., Erm. 2,404,090

GUN VTURRET POWER CONTROL Filed April l1, 1942 8 Sheets-Sheet 2 )NVENTOR5 GEORGE W. PONTIUS:m ARTHUR P. WLSON FRANK V. KU'ZMITZ A TTORNE Y 1% 94, G. w, Pom-rus, 3D., ETAL. 2,404,090

GUN TURRET POWER CONTROL Filed April l1, 1942. 8 Sheets-Sheet 3 :NvENToRS GEORGE. NPONTIUSm.'

8 Sheds-Sheet 4 Filed April 11, 1942 G. w. |`=oN-r|us, 3D., Erm.

GUN TURRET POWER CONTROL V'."Iuly 1s,v 194e.A

July 16, 1946 @.w. PQNTIUS, 3D., ET AL,

GUN IURRET POWER CONTROL Filed April ll, 1942 8 Sheets-Sheet 5 INVENTORS EOR E w. PONT usm- BY GRTH A 5 N FRANK V. KUZM\TZ A TT ORNE Y G. W, PONTUS, BD., ET AL GUN I'URRET POWER CONTROL Filed April ll, 1942 Sheets-Sheet 6 July 16 946 G. w. Pomme, 3D., ET

GUN TURRET POWER CONTROL Filed April 1l, 1942 8 Sheets-Sheet 7 NVENTRS my le, w46.

f G. w. PQNTIUS, 3D., ET AL Awww GUN TURRET POWER CONTROL Filed April 11, 1942 s sheets-sheet s am am 2 R4 U5 524 M2 @de Fm @er Patented July 16, 1946 UNITED STATES PATENT OFFECE.

GUN TURRET POWER CONTROL Application April 11, 1942, Serial No. 438,602

9 Claims. 1

This invention relates to controls, and more particularly to electrical power systems for oontrolling the movements of a gun turret.

This invention will be described with reference to a retractable turret for the lower surfaces of airplanes and with reference to a turret for the upper surfaces of airplanes. A lower turret in which the invention is used is described in more detail in application Serial No. 391,911J led May 5, 1941, on behalf of George W. Pontius.

One of the most important considerations in a power system for gun turrets is that of speed control. The gunner must have any speed necessary to keep his guns trained on a target. Further, this control should simply be obtained by a single manual control grasp for rotation in azimuth and elevation.

It is an object of this invention to provide a power control for turrets having complete control oi speed over a working range.

It is an object to provide the power controls with a selective two-step application of power to increase the range of sensitivity of the control.

It is an object to provide a control for electrical motors wherein intermittent shots of current of variable duration and of the full available voltage are applied for speed control.

Other objects and advantages of the invention will be apparent in the following description and claims.

In the drawings forming a part of this speciiication:

Figure 1 is an isometric view of part oi a turret with which the control of the invention is associated with certain parts of the turret being shown in isometric section, and certain other parte being shown schematically;

Figure 2 is an isometric view of the control box which regulates the direction of rotation and the speed of the electrical azimuth and elevation motors, part of the shell being broken away to show the inner structure of the control system;

Figure 3 is an isometric view of a detail of the control box, showing a rotating drum forming part of the control mechanism;

Figure 4 is a phantom View showing part of the turret in dotted outline having superimposed thereon in full lines a simplied version of the electrical control system for the azimuth and elevation motors;

Figure 5 is a phantom view showing the turret in dotted outline having superimposed thereon the complete electrical control system in full lines for the azimuth and elevation motors, the

2 system including automatic indexers and limit stops for retraction of the turret;

Figure 6 is a schematic isometric projection of the mechanical parts and movements of the turret;

Figure 7 is an elevation view of the rear of the control box for the turret;

Figure 8 is a plan View in section of the control box along the line 8 8 of Figure '7;

Figure 9 is a detail side view of the control box showing the shape and construction of the rocker arms which vary the electrical impulses;

Figure 10 is a sectional view of the control box showing the breaker cams and taken along the line i-I of Figure 7;

Figure 11 is a detail sectional view of the control box showing the elevation control cam taken along the line II-H of Figure 8;

Figure 12 is a simplied wiring diagram of the power circuit, showing parts of the turret in dotted outline and having superimposed thereon in full lines a modified power circuit; and

Figure 13 is a complete wiring diagram o the power circuit.

The mechanical parts relating to the movement of the turret are shown in diagrammatic form in Figure l wherein the turret is shown in an extended position. The turret |632 as a whole is supported on a four-armed spider i ifi which is `secured to structural members such as H5 of an airplane, not shown, and which has a central collar Ht. Ball bearings such as H8 rotatably support an internally threaded sleeve |29 within collar H6, which sleeve has an upper ring gear portion 22. A threaded column |24 is threaded into sleeve i2@ and is thereby supported within spider H4. A head unit 26 rotatably rides on the upper end of column 2fa' and is itself restrained from rotation by a telescoping yoke member |22 secured to the outer end of one arm of spider |14.

A single power source is used to rotate the sleeve |20 in order to rotate the turret in azimuth or optionally to retract and extend the turret. This power source is an electric motor |30 suitably secured to 'the spider Hd. The motor |30 drives a motor shaft itil to which is secured a worm |36. Worm |36 engages a worm wheel |33 which is secured to a drive shaft M3 having suitable bearings which will be later described. A worm |42 on shaft M9 engages ring gear |22, causing the sleeve lii to rotate within spider collar H6. Through the gear train thus described, electric motor |39 is made to rotate sleeve |20. The motor |39 can be reversed by 3 reversing the field current, thus reversing the direction of rotation of sleeve |20. The gear train provides a large reduction in rotation allowing the use of a very high speed motor, to provide a high power to weight ratio.

The column |25, and thereby the turret also, may be rotated in azimuth or retracted and/or extended, by selectively connecting column |2f| with sleeve |20 or with non-rotatable head |25. This selective connection is performed by an L- shaped key Ulli held in a hole through column |24 and selectively engaging an internal notch |50 in sleeve |20, or an external notch |52 in nonrotatable head |26. The mechanism for moving key |45 will be described later.

When key |513 engages notch |52 in non-rotatable head |25, column |24 is restrained from rotation. If motor |30 now rotates ring gear |22,

and thereby sleeve |20, the column |24 will4 be raised or lowered according to the direction of rotation of sleeve |22. The head |25 is lowered or raised with column |25, and the yoke member |28 will telescope and extend and will act at all times to keep head |26 from rotating. In this way the extension and retraction of turret |02 is accomplished. When the turret it is extended the key |55 may be moved to engage notch |50 in sleeve and the column |213 will rotate as sleeve |20 rotates, and thus provide the operative movement of rotation in azimuth. It will be noted that in such case the key M5 will be out of notch |52 and there is no restriction on the move ment in azimuth. The column |24 can be rotated continuously in either direction for any given number of rotations.

Certain parts of the turret are fastened on the lower end of column |2Ll. These parts include a rotatable shaft |53 to which the guns I0 are secured. The details of construction for afxing the guns to shaft |55` will be later described. A worm wheel sector |570 is secured to shaft |56 and is engaged by a worm screw |52 fastened to a drive shaft |65. Drive shaft ld in turn is driven by a worm wheel |66 secured thereto, which is driven by a worm |68 secured under Some Conditions in using breaker points to a motor shaft |10 of an electric elevation motor |72. IIhe driving mechanism described is preferably positioned within a frame or housing as will be described later.

.Also shown in Figure l an elevation gearing system for limit cams. Connected to motor worm wheel |55 is a shaft Hl having a worm |'|'|a secured to the outer end thereof. Worm |'|'|a drives a worm wheel 6|2 which in turn drives a shaft 5M. Fastened to the end of shaft Gld are cams 505, 558 and 5|0. These cams rotate in multiplied synchronism with the elevation movements of the guns.

The elevating gear train and its actuating motor are adapted to elevate or depress the guns, depending upon the direction of rotation of motor |72, which is reversed by reversing its eld. The guns ||0 can be elevated above horizontal as far as is permitted by the shape of the airplane in which the turret is mounted, and can be depressed to point straight down. The elevation arc as will be described for purposes of illustration, will be limited to a 90 arc from horizontal to vertical.

The control box 500 for the direct current electrical circuits is shown in Figure 2. It has been found that the control of two related movements, such as rotation of the turret in azimuth and elevation of the guns, can best be accomplished when a single control member regulatesboth movements. The reexes of the operator or gunner are more accurates when all movement is with one limb, rather than wtih the independent action of several limbs. The construction of the control box 500 is based on this principle, and movement of the handle 504 alone controls rotation in azimuth and elevation and depression of the guns. v

The control box 550 varies the direction of rotation of theazimuth and elevation motors as well as the speed in either direction. The direction of rotation is changed by changing the polarity of the motor fields. The speed is varied by changing the amount of the armature current while maintaining the field currents constant. In the past it has been customary to use rheostats to get a variable potential and thus to obtain a variable armature current to vary speeds of motors. This type of regulation is inherently wasteful as any flow of current through a resistance creates heat, which is wasteful of current. This is a serious consideration on aircraft where electrical energy may be supplied by batteries which are heavy and therefore must be reduced to a minimum. Another drawback of rheostat control of motors is that of poor performance under varying loads. As the load increases on a motor for a given field and armature current, such as happens when the guns are swung into the wind stream, the current in the armature tends to become greater, due to reduced speed, but this increases the I. R. drop across the rheostat giving lower voltage across the armature. Thus when the need for current is the greatest the supply is the smallest.

The present control supplies intermittent shots of current under full voltage to the motor armatures to regulate motor speed. Thus the speed can be altered by changing the frequency and/or the duration of the shots, but we prefer in the present control to have the frequency remain constant and have the duration of the Ishots varied. Ordinary breaker points are unsuited for this type of control as the almost continuous arc developed rapidly melts them. The present control avoids such a drawback and will now be described.

Referring to Figure 3, current from a suitable source is supplied to one end of a rotatable drum 5|2 by a brush 5M. The drum has conductor segments 5|5 on its cylindrical face which are in the form of a truncated triangle. These segments are placed diametrically opposite each other on opposite ends of the cylinder 5 2. A part of the base of conductor segments 5|5 extends clear around the drum so as to form a continuous contact surface on each end of drum 5|2. rlhe surface of cylinder 5|2 between conductor segments is formed of a heat resisting insulator material 5|8 suoli as ceramic. The conductor segments 5 6 are electrically connected inside the drum by means (not shown) so that the current applied to one conductor segment 5|6 by brush Elfi i-s equally effective at the other conductor segment.

The drum 5|2 is mounted within control box 500 as shown in Figure 2. A spindle 5|3 passes through drum 5|2 and supports drum 5| 2 for rotation in a pair of frame plates one of which is shown at 520. The frame plates are formed o-f insulator material and are bolted to frame 522. A pulley 5|5 is secured to one end of shaft 5|3 and is driven by a V-belt 524 driven by a small pulley 520 secured to and driven by a constant speed motor 528. The pulley end of motor 528 is suspended on a lever 529 which can be moved to tighten or loosen V-belt 524 by an adjustment screw 530 held in frame 522.

The azimuth take-off at the drum for current for the azimuth motor |33 is a brush 532 held in a slider 5.33 which rides two rods 534 screwed to frame plates 523 longitudinally to the axis of drum 5|2. Brush 532 is held to drum 5i2 by a spring 535 held in a recess in slider 533. The take-oil brush 535 for the elevation motor H2 is identical in construction to the azimuth brush. Detailed showing of brush 535 in frame 27 has been omitted for simplicity and it will not be described iurther than to say that while brush 532 contacts drum 5| 2 from above the elevation brush 535 as may be, seen contacts said drum 5|2 from the side.

The azimuth brush 532v and the elevation brush 536 are moved over drum 5|2 by control handle 504 to get varying amounts of Contact with the conductor segments 525. A bushing 538 is secured tothe top of control box 555 and round stem 545 is fitted therein having an annular flange 54|. Control handle 543 is rotatably mounted on an ear 552 of stem 5x5, and has an integral hollow shank 543 on which is secured a pinion 544 by a nut Control handle has a thumb button 553 which shunts out a resistance to give more current. It also has hump 505 of flexible material covering a dead-mans switch which cuts olf all power to the `system when the gunners grip is relaxed on handle 552. A flexible conduit 545 passing through hollow shank 543 contains the wires for the shunt switch and the dead-mans switch.

Clamped to the bottom end oi vertical stem 540 is a yoke arm 543. Its outer or yoke end (shown dotted) embraces a projection of slider 533. 533 along the length of the drum according to the swinging movement of handle 554. A wire 5 connected to brush 532 comes out the top of slider 533 and extends along transverse arm 543 to a convenient point where it can be led out of the control box 53E) to azimuth motor 35 as shown in Figure 4. .A switch (not shown but later de scribed) is actuated by the yoke arm 542 as it passes center to reverse the direction of the field of azimuth motoy i313. This switch causes rotation of the azimuth motor |35 in one direction for one end of drum 5 I 2, and rotation in the other direction for the other end of drum 5|2.

Sliding elevation brush 536 along drum 5|2, is accomplished by rotation of handle 534 about its axis. as contrasted to swinging about stem 54D for control of the azimuth brush 532. For this purpose a square bar 550 having a rack 552 on one end is inserted in a square longitudinal hole formed in stem 545. Rack 552 meshes with pinion 544| on handle 554'. Bar 555 extends below the bottom of stem 545 where, through a swivel connection 554, it supports a lower bar 555 guided in a frame 522 and having a rack 553. Rack 555 meshes with a pinion 558 secured to a shaft arranged transversely to bar 555 and journalled in frame 522. A yoke arm 554 is secured to the end of shaft 552 opposite to the gear 55B. The arm 584 moves the slider for elevation brush 535 in a manner identical with that in which the azimuth brush 532 is moved. A wire 4 leads from elevation -brush 535 out the top of its slider and down yoke arm 562 to a point where it can be led out of box 550 and down column |24 to the elevation motor |72. A switch (not-shown but Thus swinging of handle 554 moves slider later described) is actuated by yoke arm 534 everytime it passes dead center and this switch reverses the field of elevation motor |72 to reverse its rotation.

The operation of the control box of Figure 2 with respect to the turret is as follows. Assumeing that the turret is extended ready for combat, the gunner will grasp handle 55d pressing hump 505 and thus passing power to the entire turret and to the control box including brush Elli (Figure 3') contacting drum 5|2. The motor 525 will be energized and cause drum 5|2 to rotate. If the gunner desires to rotate the turret to the right, for example to train the cross hairs in the periscope on a target airplane, he pushes the handle 554 causing it to rotate clockwise on stem 545. This movement causes arm 558 to move clockwise also so that brush 532 contacts the right conductor segment 5l5 (Figure 3), contacting first the inner narrow end of the segment.

While touching just the narrow inner end of conductor segment 5|5, an intermittent current is sent to azimuth motor |30- which is composed of short shots of current and relatively long intervals in between. Under these conditions the motor |35 will move very slowly and the turret will rotate at an almost imperceptible rate. If the gunner desiresV more speed he push-es the handle 504 further so that brush 532 will contact a wider portion of conductor segment 5i5. The intermittent current will then have longer shots of current and correspondingly decreased intervals between, and under these conditions the motor |35 will rotate at a moderate speed. If still further speed is desi-red the handle` 555s is pushed as far as it will go so that brush 532 contacts the continuous conductor band at the end of drum 5|2, resulting in a continuous flow of current to azimuth motor |35. If still further speed is required the gunner presses button 553 on handle 504 and this shunts out a resistance in series giving the drum 5| 2 the full available voltage and current.

To rotate the turret to the left the gunner pulls handle 534l toward him, causing it to swing counterclockwise about stem 540. As yoke arm 548 passes the midpoint on drum 5|?. it actuates a switch which reverses the eld of azimuth motor |35 reversing the direction of rotation. The brush 532 may then be moved to any point on the left end of drum 5|2 that gives the desired speed at the particular time.

To depress the guns HG, at any timey whether the turret is rotating or not, the gunner twists the handle 554 oven rotating it clockwise as viewed from the right in Figure 2. This movement causes brush 53B to transverse the right hand part of drum 5|2, and the speed regulation is the same as that described for the azimuth brush 532. To elevate the guns the handle 554 is twisted under, rotating in counterclockwise as viewed from the right. As yoke arm 553 passes the centerpoint of drum 5|2 it actuates a switch which reverses the field of elevation motor |72 reversing its direction of rotation. Thereafter current taken oil by brush 535 causes the guns to be elevated.

If the turret is extended and it is desired to retract it, the guns H0 are elevated by twisting handle 554, until the guns are horizontal. The turret is then rotated to the right until the guns approach the rear of `the airplane, by pushing handle 504 forward about stem 555. When during rotation the guns reach the rear, the connector key |44 (Figure 1) will connectvthe col-V 7 umn |24 to non-rotatable head |26. Further ro` tation of azimuth motor |30 will cause sleeve to rotate and screw the turret up into the airshp in which it is mounted. To extend a retracted turret the gunner pulls handle 504 toward him causing azimuth motor |30 to rotate sleeve |20 and in opposite direction and screw the turret down. At the lower limit of extension the key |44 connects column |24 to sleeve |25 and the turret starts to rotate and is ready for combat.

The control box 56E] gives reliable and accurate performance. Any arcs are extinguished on drum 5|2 as the brush moves from conductor 5| 6 across the insulator 5|3. Further, when traveling from conductor to insulator there is a gradually reducing current through the brush so that the final break is only of a relatively small current thus reducing arcing as compared to ordinary breaker points. Any desired type of speed increase curve 'is possible by merely shaping the conductor segments 5 i S as desired.

The power circuit for the turret is shown in simplilied form in Figure 4. Since Figure 4 is a simplied drawing parts are omitted in certain cases for simplicity, but the basic wiring system may be traced also on Figure 5 which shows the complete power circuit. Parts of the control box 500 can be identified in Figure 13, The rotating drum 5|2 and its driving motor 528 are shown in dotted outline, as well as the control box handle 534 near the top of the drawing.

Current is supplied to the turret by a battery or storage cell BI giving about 24 volts, although a D. C. generator could just as well be used. Battery BI is grounded at one terminal to the frame of the turret, and the other terminal is attached to a wire which leads -to a relay Ll.

A wire 2 leads from relay Ll to series resistance f RI, the function of which will be described later. A wire 3 leads from resistance Rl to brush 5|4 contacting drum 5|2 where the current is distributed to azimuth brush 532 and elevation brush 535 as explained with reference to Figures 2 and 3. Wire 2 supplies current also to a wire |4 leading to motor 528 which causes drum 5|2 to rotate.

Leading from azimuth brush 532 is a wire 5 connected to the armature Al of the azimuth m0- tor |30. Elevation brush 535 delivers current to a wire 4 which passes down the central column to conduct current to the armature A2 of elevation motor |12. Through the circuits described, controlled current may pass from battery BI to the armatures AI and A2 respectively of the azimuth and elevation motors;

Also shown in Figure 4 branching from wire I is a wire which leads to a switch SI in the control handle 504. The other side of switch SI is connected to a wire which leads to relay L| which is normally open. When the gunner grasps the control handle 534 he closes switch Sl which energizes relay Ll, connecting wire to wire 2 and passing current to the whole turret. Thus no current can pass to the turret until the operator grasps control handle 554, The same circuit causes current to be cut off from the whole turret if the gunner relaxes his grip, thus providing a dead-man control. If the gunner is shot While operating his turret, he will relax his grip, opening relay Ll, and the turret will cease operation, preventing waste of current and possible injury to the turret or the airplane in which it is mounted.

Connected to wire 2 are wires 9 and 8 by which current is supplied to the iields of the azimuth and elevation motors respectively. Wire 9 leads to a two-finger, four-contact relay L3 having the two middle contacts grounded. One ringer of relay L3 is connected to a wire |6 leading to one end of the azimuth motor eld Fl. The other finger of relay L3 is connected to a wire Il which is connected to the other end of eld Fl. When relay L3 is energized it reverses the normal drection of current flow through field Fi, reversing the lield FI and thus reversing the motor |30.

Relay L3 is energized by the movement of azimuth brush 532 over drum 5|2 in the control box. Leading from wire 2 is a wire i8 which leads to a switch S3. in the control box which switch is mechanically actuated by azimuth brush 532 when it passes the center of drum 5 2 while being moved to therleit. The other side of switch S3 is connected to wire I9 which leads to relay L3 to energize relay L3. Thus for all positions of` azimuth brush 532 to the right of center, switch S3 will be closed and relay L5 will be energized to cause current to iow through eld F| as indicated in Figure 4. For all positions left of the center of the drum the switch S3 will be open, allowing relay L5 to assume a normal position which causes current to flow through eld FI in the opposite direction, thus reversing the direction of rotation of azimuth motor |33,

rlhe circuits for supplying current to the field of the elevation motor |12 are similar to those for azimuth motor |32. Wire 8 passes down the central column and connects to a two-finger, fourcontact relay L4. Connected to one finger of relay L4 is a wire 2|) leading to one side of the field F2 of elevation motor H2. A wire 2| leads from the other linger to the other side of eld F2. Wires 26 and 2| are normally connected as shown in Figure 4 but whenrelay L4 is energized it causes current flow in the reverse direction, reversing the direction of rotation of elevation motor |l2.

Relay L4 is energized by the movement of elevation brush '533 over drum 5|2. Leading from wire 2 is a wire |5 which passes current to a switch S4. Switch S4 is normally open as shown in Figure 4, but when brush 535 passes the center of drum moving right brush 53S closes switch S4, and when brush 535 is moving to the left the switch S4 is opened. Switch S4 passes current to a wire 23 which passes down the central column |24 to actuate relay L4. When relay L4 is energized, the i'leld F2 is reversed, reversing elevation motor |12.

In summary, with relation to Figure 4, the operation is as follows. The gunner grasps control handle 504 which closes switch S|, operating relay Li to pass current to wire 2, through resistance Rl and to brush 514. At the same time current passes through wire I4 to motor 528 and it causes drum 5| 2 to rotate. Current nows from brush 532 to armature A! of the azimuth motor |32 and iiows from brush 536 down the central column to armature A2 of the elevation motor. The elds F| and F2 of the motors are reversed every time their respective armature brushes y532 and 53B pass the center of the drum 5|2. When azimuth brush 532 passes center from right to left it opens switch S3, deenergizing relay L3 which then passes current to eld FI in a direction opposite to that shown in Figure 4. When elevation brush 535 passes center from left to right it closes switch S4, energizing relay L4 and passing current to field F2 in a direction opposite from that shown. When the brushes move pastcenter in the other direction their respective elds are 9j reversed and are connected as shown at relays L3 and LA! in Figure 4.

The complete power circuit for the turret is shown in Figure 5. The basic functions illustratecl in Figure 4 are included in Figure 5, but with .the addition oi more elaborate controls. Also Figure 4 is a siinplied power circuit and therefore incomplete in some respects. The circuits will now be described with relation to Figure 5.

One addition in Figure 5 over Figure 4 is the provision of a speed change switch in the conrol handle 594. Branching from wire 2 is a wire i2 leading into control handle 5de to a switch S2 actuated by push button l593. A wire i3 leads from switch SZ to a relay L2 closing a shunt circuit around resistance Rl. This shunt circuit is formed by a wire 2a leading from wire 2 to relay L2 and by a wire 3a leading from relay L2 to wire 3. Thus by closing switch S2, relay L2 is actuated to complete a shunt around resistance Rl. Shunting out resistance RI gives a greater effective voltage for the drum 552, thus giving a two-speed electrical range by closing or failing to close switch S2.

Another part of the complete power control relates to means to render the azimuth motor lili! inoperative in a retraoting direction if the turret is already retracted or when the turret reaches the top of a retraction movement. Wire I i i9, which the wire energizing field relay L3 of the azimuth motor when the brush passes the center of drum 5H? moving to the right, the retract position has a branch wire Eil. liire 24 ,casses down the central column and emerges at the bottom to connect to a retract limit switch Sc which is closed by an actuating pin 575 on spider lis when the turret is retracted. Switch Se in turn passes current to a wire 25 connected to it. which leads up the central column to a relay L5 interposed between wires 5 and il, the relay serving to break the azimuth armature current. Thus when switch Sli is closed, by the retraction movement or after the retraction is finished, no current can pass to azimuth armature Al when the brush ""'l is pushed to the retract position, to the rLht on drum 5i2. When brush is moved to the extended position current may be supplied to armature Al because wire 24 is not then energized and no current can dow to relay wire and relay L5.

Another part of the complete power control, shown. in Figure 5, relates to means to render the elevation motor inoperative when the turret is retracted. Accidental movement of the control handle while the turret is retracted would result in injury to the turret and the airplane if this provision were not made. Branching from wire 2 is a wire i5 leadito the switch member of a switch S5. This switch has two contacts, one connected to wire which leads to switch S4, the other connected to wire 2S! which passes down the central column to a relay Le.

Switch normally tends to connect wire l5 and wire which actuates relay L3 to render the elevation ino-tor il?. inoperative. When the turret is fully extended, however, non-rotatable head i255 (not shown) the top of the central column iii-1l descends upon switch S5 as the turret is extended and causes switch S5 to disconnect wire 23 from wire i5 and to connect wire 22 with wire This deenergizes relay Le allowing current to ow to armature and allowing current to flow to switch Sd to reverse selectively the elevation 'leld F2. At the slightest retraction movement the head I2@ rises and allows switch 35 again to connect wires l 5 and E?, causing relay L6 to break the connection to armature A2, insuring that the guns will remain horizontal at all times during and after retraction and while extending the turret.

Before the turret can be retracted the guns must be elevated t0 a horizontal position so that their inner ends will not strike parts of the turret when retracted. The retracting circuit is accordingly rendered inoperative by the retract index cam 5536 which is synchronized in elevation with the guns llo of the turret. A branch from wire 8 at the lower end of the turret, wire 25 conducts current to a switch S7 which is actuated by retract index cam EBS in the elevation compensator WG. Index cam 5&5 keeps switch Sl normally closed and opens it only when the guns are horizontal, at which position the cut-away portion allows the switch S1 to open. The other side of switch Si is connected to wire El which leads up the central column to switch S3 at the control boX.

It will be noted that inside the central column and at the top there is a wire branching from wire 25 and leading to a switch S8. A wire 35 leading from wire 2l' is connected to the other side of switch S3. Switch S3 is the retract lever switch, and is closed whenever retract lever, not shown in this application, is actuated to retract the turret. The operation of the retract lever has been fully described in Pontius application Serial No. 391,911, led May 5, 1941, and Pontius et al. application Serial No. 497,468, led August 19, 1941. If the turret is extended and the gune ner tries to retract it while the guns are other than horizontal, current will flow from wire 2 to 8 down the column to wire 28, through switch Sl to wire 2l, up wire El to Si?, through switch S3 to wire 29, into wire 25 to relay L5, where the current breaks the contact between wires 5 and t and n-o current flows to azimuth armature AI and the turret will not retract. If the guns are horizontal and the gunner operates the retract lever, switch Sl will be open and no current will flow across switch Si! to energize relay L5, and retraction will take place when current ilows to armature Al Switch Si; also serves another function: that of insuring that the azimuth motor will not turn in a direction to extend when it is desired to retract the turret. If this provision were not made, the central column would be jammed against the rotatable threaded sleeve i243 which retracts and extends the turret. It will be remembered that when the turret is ready for retraction the gunner will close retract lever and switch S3 by actuating the retract lever in a manner described in the two applications referred to in the pare.- graph above, and the guns will be horizontal thus opening switch S1 and preventing ow of current to wire 2i at that point. rThis safety function is accomplished by a circuit through the upper end of wire 2l which is connected to switch S3. When the azimuth brush moves to the left part of the drum (extend and rotation-to the-left) switch S3 is actuated to cause current to ilow from wire lil to wire 21. Current will then /ow into wire 2l at switch S3, int-o wire 35, through switch S3, down wire 29 to wire 25 and through wire 25 to relay L5, which breaks the current to armature Al of the azimuth motor i3d preventing extension of the turret. Thus the circuit just described provides a safety cut-out of the retracting motor IBG if the gunner should .switch S3.

ll inadvertently move the azimuth brush 532 in the wrong direction for retraction.

The circuit just described also insures that the gunner will not have his fingers injured by the rotating turret when he is manipulating the retract lever. As shown in Figure 10 of Pontius application Serial No. 391,911, the gunner presses on the right side of the retract lever to move it to the left for retraction. If the turret, instead of rotating to the right as it must to retract, should rotate to the left, his ringer would be wedged between the stationary head rest support and the retract lever (Figure of Pontius application Serial No. 391,911) as the lever rotates counterclockwise with the turret. The safety circuit described in the foregoing paragraph prevents this from happening and insures that the turret will always rotate tothe right or clockwise for retraction, which movement would lift the gunners linger ol'f the lever if the turret did not lock at the straight back or rear position at the time of actuation of the retract lever.

When the turret is retracted and the gunner desires to extend it, he does not actuate the retract lever, but merely moves azimuth brush 532 to the left part of drum 5&2. This causes azimuth motor 33 to rotate sleeve 23 to the left or counterclockwise screwing the turret downward. The safety circuit, effective in retraction to prevent the azimuth motor from rotating sleeve |20 to the left, is not effective during extension because the retract lever is not actuated and the retract switch S8 is open. When the turret is fully extended the connector key |44 (Figure l) slips into notch |50 in sleeve |20 and the turret rotates to the left, ceases extending, and is ready for use.

The remaining Controls and circuits of Figure 5 relate to the upper and lower limit stops for the guns l IQ of the turret in elevation and depression. This function is likewise accomplished by cams synchronized with the movement of the guns. Lower limit cam 528 in the elevation compensator H3 has a notch cutin a position with relation to an actuated switch S3, corresponding to the straight-down position of the guns which is the lower limit of depression. Upper limit cam 5&0 also in the elevation compensator box, has a notch cut in a position with relation to an actuated switch S l 3, corresponding to a horizontal position of the guns H13, which is the upper limit of elevation.

The lower limit switch S9, actuated by the lower limit cam 5&8 is connected on one side to wire 23, which is the Wire energized at the control box whenever elevation brush 535 is moved to the right or to a depression position on drum 512. Therefore, while the guns are being depressed, wire 23 will be energized passing current to The other side of switch SS is connected to a wire 3i which-leads to eld control relay Lil, energizing it to reverse the current to field F2. At all points on the elevation arc, except for the straight-down or lower-limit position, the lower-limit cam 538 will keep switch S9 closed, energizing held control relay LQ when energy is passing into wire 23. As shown in Figures l and 5, the elevation brush 53E is in an elevation position and current does not iiow into wire 23, and relay L6 is inactive even though switch S9 is closed.

The lower-limit stop cornes into operation when l the gunner twists the control handle 504 oven causing the elevation brush 536 to contact the right hand side of drum 5l2. This movement passes current into elevation armature wire 4 as well as passing current into wire 23. At lower limit switch SS, current passes into wire 3l from wire 23 and energizes relay L4 which passes current through the eld F2 in a direction to cause motor |12 to depress the guns when current iiows through the armature A2. If the depression of the guns continues they will soon be pointing straight down, the lower limit of their elevation arc. At this point cam 508 rotates so that the notch is opposite switch S9 which then opens, deenergizing th'e relay Lft and causing motor i212 to reverse its direction and elevate the guns. If the gunner persists in having the controls in a depressed position, the gus will elevate only until cam 508 closes switch S9 again and reverses the field. Thus the guns will continue to alternate between elevation and depression at the lower limit if the controls are kept in a position to depress the guns.

The circuit for stopping the guns at the upper limit of their arc is actuated by upper limit cam 5H). It will be noted that the notch in upper limit cam EIS has the the same relative position as the notch in cam 536, and this is because the upper limit of the guns happens to be at the horizontal position which is the position of the guns when the turret is retracted. As stated earlier in this description, the guns could be elevated above horizontal if it were desired, and in this case the notch' of upper limit cam 5I!) would be placed at a more advanced point.

Upper limit cam 51E! actuates switch Si@ which connects wires 23 and 26. Wire 26 is continuously energized because it is a branch of wire 8. When wire 23 is energized it can pass current through switch S9 to actuate relay Ld. As explained above, lower limit cam 508 keeps switch SS closed at all points on the elevation arc except the bottom point, and for this reason switch S9 is closed at all times whenever it is desired that the upper limit stop circuit be effective. Switch SI which passes current from wire 23 to wire 23, is normally open, and is closed only when the guns are horizontal at which position the notch in upper limit cam 5H) allows the switch SIG to close.

While the guns are being elevated brush 536 will be on the left part of drum 5l2 and switch S4 will be open so that no currentpasses to wire 23. At the lower end of the turret, switch' SH3 will normally be open so that no energy passes to wire 23 at that point. In such case, although switch S9 is closed, no current flows to relay Ld and it connects the field F2 as shown. As the guns are elevated by the armature current flowing through brush 536 and wire Il, they approach the horizontal and at that position upper limit cam 5m allows switch SIU to close. Current now ows from wire 26 through switch Sl 4to Wire 23, through switch S9, and through wire 3i to energize relay L4 which will reverse the ield F2, causing the guns to change direction and depress rather than elevate. When the guns have been moved in a depression a short distance, upper-limit cam 5m moves accordingly until its notch opens switch Si. This breaks the circuit to relay LA and the eld F2 is again reversed, and the guns once more start to elevate. Thus if the gunner keeps brush 536 on the elevation end of drum 5I2 the guns reach the upper-limit posi'- tion, which is horizontal, and alternate up and down in a limited arc governed by the amount of rotation of cam 5H] necessary t0 open and close sWitch'Sl.

The operation of the lower turret is as follows.

Assuming that the plane, not shown, on which the turret is mounted is flying and the turret is in its retracted position when an enemy plane is sighted or suspected, the gunner will iirst wish' to extend the turret. Thereupon, he grasos handle 5514 closing switch Si and passing current 'to the turret, and swings handle 59e toward himself causing brush 532 to move to the left part of the drum EEE. This nio-vement causes switch S3 to disconnect wires I8 and i9 and current is no longer supplied from wire IS to branch wire 24. rfhus current can no longer flow from wire 24 through switch S to wire 25 into relay L5. Current passes to armature AI and wire i9 no longer passes current to field relay .L3 and the relay is deenergized to connect field Fl in an extend direction.

.Azimuth motor l now causes sleeve to rotate to the or counterclockwise and turret is extended. The sgoeed with which the turret is extended depends unon, first, the distance which control handle 5&4 is Aswung and the consequent distance that brush 532 is moved away from .the center of the drum 5 l 2 as explained in connection with Figure and second, by operation of the button 533 on handle giving to the drum 5|2 the full available voltage and current. As the turret nears the bottom of the extension stroke, connector key i 44 slides vertically past the top of sleeve E28 because it is held within that limit by pin lli. Further extension causes a pin (not shown) to strike the top of sleeve |26 and the pin is pushed up into itsrecess. .As the turret reaches the inal limit of extension notch lei! in sleeve to rotated opposite key lil-'l and a spring pushes key 544 into that notch. The turret now starts to rotate and the gunner is ready for comhat.

The final extension of the turret causes head |2S (Figure 5) to contact switch S5, causing it to disconnect wire from wire |5 and to connect wire 22 to wire i5. lifire 2d being no longer energized allows relay L6 to he deenergized and the current may now now to elevation armature Ai. Wire i12 passes energy to switch S4 allowing that switch to actuate to iield relay through wire 23, switches .S9 and Sill and wire 3 l.

More sneciiically and referring particularly to Figures e and 5 for the electrical circuit and to Figure 1 for the mechanical parts and movement there follows a more detailed description of the operation of the turret during combat.

The turret is shown in an extended position ready for combat in Figure i.. The connector key i442 (Figure 1) is urged outwardly by a spring so that it nts notch |554 in sleeve |29, causing column i243 to rotate with sleeve E2G. To operate the turret the gunner grasps control handle 594 (Figure 5) closing switch Si, and thereby closing relay Ll to pass current to the turret from battery Bl. Il the gunner desires to rotate the turret to the right, or clockwise, he swings handle 531i away from himself causing azimuth brush 532 to move to the right end ci drum 5 2.

This movement of kazimuth brush 53.2 causes cur from it through wire through relay LE and wire d to the azimuth motor armature Al. The same movement of brush 53.52 closes switch S3 which passes current from wire |8 to wire lil and through wire la? to held relay L3 which connects the azimuth held FI in a direction to cause motor Hitt to rotate to the right or clockwise, Motor i3@ drives its shaft i34 to which worm screw is attached. Worm screw |36 drives worm wheel |33 which is attached to drive 14 shaft |49. Drive shaft |40 drives worm screw |42 attached thereto, which screw meshes with and drives ring gear |22 attached to sleeve |20. Sleeve |20 is thus rotated, and acting through connector key |45 (Figure l), drives the column |24 in rotation in azimuth.

If the gunner desires to rotate the turret to the left 01 counterclockwise, he swings the control handle 594. toward himself causing brush 532 to contact the left part of drum 5|2. In this position current will again pass from brush 532 through wire 5, through relay L5 and wire 6 to armature Ai. The movement oi brush 332 to the left opens switch S3 so that current no longer flows from wire I8 to wire i9, and the eld relay L3 will le deenergized, allowing the field wires i and l? to pass current through eld FI in an opposite direction, reversing the direction of rotation of the motor |313. The motor |30 then acts through the azimuth gear train to rotate the turret to the left or counterclockwise.

If the gunner desires to depress the guns ||0, he twists the control handle 5M over or rotates it on its axis in a clockwise direction as viewed from the right end. This movement causes elevation brush 536 to move to the right part of drum 5i2, passing current through wire 4 which passes down the column to relay through relay Ld and through wire l to the elevation arma ture A2. The movement of brush 53S to the right closes switch S4, passing current from wire 22 to wire which leads down the central co1- umn to switch in the elevation compensator, through switch and wire 3| to relay L4. Relay Ld when energized connects the field F2 in a direction opposite from that shown, reversing the motor il?. Motor il?. drives its shaft lli! to which is attached worm screw |63. Worm screw drives worm wheel idd attached to drive shaft |64, which shaft also has worm screw H32 attached to it. Worm screw 5&2 in turn drives wheel sector ltd attached to gun shaft ld on which the guns are mounted, depressing the guns as wheel sector it rotates.

If the depressing movement of the guns continues the guns will reach the lower limit of the elevation arc, the straight down position, rhis depressing movement causes worm wheel |56 to drive shaft il? (Figures l and 5) which has a worm Illu driving compensator worm wheel 5|?. Worm wheel 552 in turn drives compensator shaft 524 to which secured cams 508, and Eli). When lower limit cam is rotated to a position corresponding to the lower limit or straight down position of the guns, its notch allows switch S9 to onen breaking e current through wire 3| to relay Ld. Field Fl is then reversed, causing the guns to start to elevate. When the guns have elevated a small amount, cam 563 will rotate in synchronifm closing switch SQ and the guns will start to depress. Ihus when the controls are kept in the depressed position the guns will alternate at the lower limit between depression and elevation in a small arc governed by the amount of rotation of 5&2 necessary to close switch SQ.

If the gunner desires to elevate the guns he twists handle 5de under or counterclockwise when viewed from. the right end. This movement causes elevation crush to contact the left end of drum and current lows from brush 535 to wire 23. The movement to the left opens switch S4 so that no current can to wire 23 down the column to switch SQ and relay L4.

Thus relay L4 is not energized at switch S4, the field is reversed from that required for depression, and the motor will act through the elevation gear train to elevate the guns.

When the guns reach 'the upper limit of the elevation arc, cam 5|!) will allow switch S|0 to close, passing current from wire 26 to wire 23, up wire 25 to switch S3, which is closed when switch SN is eiective, through switch S3, and down wire 3| to eld relay L4. When relay L4 is energized it reverses the direction of field F2, and thus motor |12, and the guns begin to depress. Cam 5|0 rotates accordingly and after a short movement opens switch Sl causing relay L4 to once more be deenergized and the guns will elevate. Thus the guns will alternate between elevation and depression if the controls are kept in the elevating position.

The triangular conductor segments 5 i on drum 5|2 (Figure 3) allow speed control of the elevation and azimuth motors. The control handle 504 can be moved to give movement in azimuth and elevation at the same time and at different speeds. The stops of the upper and lower limit of the elevation arc are automatic. There are no stops in azimuth because the turret is free to rotate for any given number of rotations in either direction.

When the gunner desires to retract the turret he must place the guns in a horizontal position and he twists or rotates control handle 555 under to accomplish this. When the guns Hi! reach horizontal the gunner should stop them. However, when the guns do reach this position they will oscillate back and forth slightly so that it is not dicult for the gunner t stop them. After the guns are horizontal he presses the retract lever which has been more fully described in Pontius application Serial No. 391,911 and Pontius et al. application Serial No. 407,458, assuming that the guns are pointed toward the rear so that retract lever is on the inner side of column |24 near him. Pushing the retract lever for retraction closes switch S8 at the top of column |24, causing it to connect wire 2 to wire 25 leading to relay L5. At the same time the gunner will rotate the turret to the right, which is the direction of rotation of sleeve |20 necessary to screw the turret up into the airplane to retract it.

As the turret rotates the guns toward the rear, key l44 will come opposite notch |52 (Figure 1) in nonrotatable head |26. The pressure of the gunner on the lever will act to pull the key |24 into notch |52, locking the column |24 to head |25, preventing it from rotating. As sleeve |23 continues to turn to the right or clockwise it will screw the turret up into the airplane in which it is mounted. When the turret nears the upper limit of its retraction, actuation pin 513 (Figure on spider I4 closes switch S5, passing current from wire 24 to wire 25, which leads up the column to relay L5. This causes the relay L5 to break the current to armature Ai and the sleeve 20 ceases to operate.

As the turret retracts, non-rotatable head |26 rises with it. The slightest upward movement of head |26 allows switch S5 (Figure 5) to connect wire l5 to wire 28, passing current to wire 28 which leads down the column to relay L3. Energizing relay L6 breaks the current to armature A2, preventing movement of the guns in elevation during retraction, after retraction and while extending, This provision insures against injury of the turret if the controls are accidentally moved to elevate the guns while the turret is other than in a fully extended position,

If the guns are not horizontal when the gunner tries to retract the turret by pressing on retract lever |56, which closes switch S8, the turret will not retract. Switch S`| will then be closed, passing current from wire 26 to wire 27, which passes current up the central column to switch S8. Switch S3 passes the current to wire 25 which leads out of the top of the column to actuate relay L5 to break the current to armature Al. Thus if the guns are not horizontal when retraction is attempted the azimuth or retracting motor will be automatically stopped.

If the gunner desires to extend the turret, he does not operate the retract lever, but merely moves azimuth brush 532 to the left part of drum 5|2. This movement causes switch S3 to disconnect wires I8 and I9, and branch 24 from wire i3 is no longer supplied with current. Current can no longer flow from wire 24 through switch S6 to wire 25 and thus to relay L5, and relay L5 is deenergized allowing current to pass to armature AI. Wire I9 no longer passes current to eld relay L3 and it is deenergized to connect iield FI in an extend direction.

Azimuth motor |30 now causes sleeve |20 to rotate to the left Vor counterclockwise and the turret is extended. As the turret nears the bottom of the extension stroke connector key |44 slides vertically past the top of sleeve |20 because it is -held within that limit by pin |55. Further extension causes pin |54 (Figure 6) to strike the top of sleeve |20 and the pin is pushed up into its recess. As the turret reaches the iinal limit of extension, notch l5!)v in sleeve |25 is rotated opposite key |44 and spring |4461, pushes key |44 into that notch. The turret now starts to rotate and is ready for combat.

The final extension of the turret causes head |26 (Figures 1 and 5) to contact switch S5, causing it to disconnect wire 28 from wire l5, and

Y to connect wire 22 to wire I5. Wire 28 being no longer energized allows relay L6 to be deenergized, and current may now flow to elevation armature AI. Wire 22 passes energy to switch S4, allowing that switch to actuate the held relay L4 through wires 23, switches S9 and SIB and wire 3|.

The mechanical parts and movements of the upper turret 202 are shown schematically vin Figure 6. At the bottom of the gure a high speed electrical motor 228 drives a motor shaft 230 to which is secured a worm 232. Worm 232 drives a Worm wheel'234 secured to a drive shaft 233 to which is secured at the other end a driving Worm 23B. VDrive worm 238 engages a worm wheel 240 secured to rotatable column 258, and drives column 203 in rotation in either direction depending upon the direction of rotation of azimuth motor 228.

VThe gear reduction between compensator worm wheel 245 and worm 2133 is the same as that between column worm wheel 240 and driving worm 238, resulting in compensator` shaft 248 rotating one revolution for every revolution of column 208 and rotating in synchronism.

Rotatable column 208 is preferably made of aluminum or magnesium to reduce weight. The frame 2| 0 secured to the top of column 208 is also preferably magnesium or aluminum and may be made by casting. An opening 2H in the frame 2|0 provides a place wherein the gunner may position himself to operate the turret. The guns 2 I2 are secured to a rotatable gun shaft 244 supported near each gun by frame brackets 213.

Gun shaft 244 is driven in elevation by a high speed electrical motor 241 positioned within a well 2139 in frame 2id. Motor 241 drives a motor shaft 249 to which is secured worm 25D engaging driving worm wheel 252 mounted on a drive shaft 254. Secured on the other end of drive shaft 254 is a driving Worm 254 engaging a worm wheel sector 253 secured to gun shaft 254. The gun shaft is rotated in either direction by reversing elevation motor 241, elevating or depressing the guns according to direction of rotation of motor 241.

The elevation compensator drive is obtained through abevel gear 252 secured to shaft 244, and driving a matching bevel gear 264 which drives elevation compensator shaft 266. Fastened to compensator shaft 226 are limit cams 412, 414, 4| 6 and 4|8. Since the elevation movement of the guns is about 90, the ro-tation of compensator shaft 265 is multiplied about three times to increase sensitivity of the cam control.

The control box 444 for the power` system of the upper turret is shown in Figures 7, 8, 9, 10 and 11. Figure 7 shows a rear view of the control box showing a cover plate 426 to which the mechanism of the entire box is aixed so that the whole unit may be removed from column 248 in one unit. Secured to plate 42S is a frame 428 which supports the inner ends of the control mechanism. Secured to frame 428 is an electric motor 438 having a fan 432 secured to one end and a pulley 434 secured to the other. Through a drive which will be later explained, the motor 434 causes a shaft 441) to rotate at a constant speed. Mounted on shaft 44D are eccentric cams 442 which strike breaker arms 444 pivoted to a rod 445 and urged in a clockwise direction by a spring 448 secured to frame 423.

Current is grounded through breaker arm 444 from relays which then act to interrupt the current as will be later explained. Breaker arm 444 breaks against a grounded Contact 450 held in a curved arm 452 also pivoted to rod 445. Since the free stroke and the frequency of breaker arm 444 is a constant the duration of contact of breaker 444 and contact 45t is varied by varying the position of contact 45t? with re spect to the stroke of arm 444. In this way the breaker arm 444 may touch contact 454 at an intermediate point in its cycle of movement and remains in contact until the cycle of movement again lifts it free. As shown in Figure '7, the contact 454 is in the neutral position wherein there is continuous contact with the b-reaker arm causing the actuated relays to remain continuously open so that no current flows to the motors.

The positioning of contact arm 452 is accomplished by a lever 454 pivoted on a rod 456 and having an adjustable screw 453 touching arm 452. tretched between contact arm 452 and lere-r 454 is a spring 44@ holding the two parts constantly against each other. lever 454 is in turn positioned by an adjustment screw 462 contacting a double frustro-conical cam 454 which is axially movable to act as a cam. The axial position of cam 444 is controlled by the gunner land in this way the gunner controls the duration of the current shots to the azimuth motor.

Between the lower end of lever 454 and frame 424 is a compression spring 4% urging adjustment screw 442 in contact with cam 4&4.

The control box 40d is seen in vertical section in Figure 8, which is a sectional View of the box tact arms 452.

from below locking upwardly. The cover plate 425 has an opening in front of fan 432, which is covered with metal screen 468. The fan 432 blows air through the screened covered opening to cool the motor and electrical contacts. The pulley 434 on the other end of motor 43B, through a belt 435, drives a pulley 433 connected to the rotary cam shaft 444.

Lever 454 is shown in Figure 8 and adjusting screw 462 is shown contacting double frustroconical cam 454. A similar lever 413 for operating the breaker .arm for the elevation motor is also shown in Figures 9 and 11 pivotally mounted on rod 4513. Lever 410 is similar in construction to lever 454 and operates in the same manner. It is positioned however by a rotary cam 412 mounted on a rotatable hollow shaft 414. This structure is shown in detail in Figure 11, where the elevation cam 412 appears in prof-lle. Shaft 414 rotates in a bushing 415 integrally formed with cover plate 424. The outer end of shaft 414 is enlarged to form a housing 41S. Control handle 402 is rotatably secured to housing 418 by a stem 43D. When the gunner pushes or pulls on handle 492 transversely to the aXis of shaft 414 he will cause the shaft to rotate, rotating cam 412 and changing the position of lever 410.

Secured to stem 486 of control handle 4t2 is a gear` segment 482 contacting a rack 484. The double-frustroconical azimuth cam 464 is secured to rack 444 and the inner end of the rack is positioned in a bushing 48S integrally formed in frame 423. Back 484 rotates with shaft 414 and consequently causes cam 454 to rotate. Since cam 444 is circular, however, there is no effect on the azimuth adjustment due to rotation of the cam. When the gunner Wishes to change the speed of the azimuth motor he merely rotates handle 442 on stem 48!! causing gear segment 482 to move the rack 454 in or out, and thereby moving cam 464.

The outlines of the control levers 41! and 454 are shown in Figure 9. It will be noted that lever 454 has two screws 458 for positioning two con- In all, there are four breaker arms 444 controlling four relays interrupting the current supply, as will be later explained.

The arrangement of the cams 442 on shaft 44K.` is shown in Figure 10. Each cam is offset 180 from its mate, to obtain alternation in the relays operated by each breaker arm 444. Also shown in Figure 10 are the levers 454 and 410. p

The control box is shown diagrammatically in` Figure 12 as applied to a simplified version of the contro-l system. The control box motor 430, the driving and driven pulleys 434 and 438 are shown in dotted outline as well as the cam shaft 440 on which cams 442 are mounted. During operation the shaft 444 is continuously rotating causing the breaker arms 444 to move regularly and to open and make Contact when not in the neutral position. rIhe control handle 442 is also shown in dotted outline and both rack 484 and shaft 414 are shown diagrammatically by a single broken line leading therefrom. The azimuth and elevati-on cams 4&4 and 412 are also shown diagrammatically as eccentric cams on a shaft. The function of cams 434 and 412 already described, that of varying the position of the grounded contact 454 against which the breaker arms strike, is also shown diagrammatically.

Current is supplied by the battery B2 to the wire 341 which leads up the column to a relay L42. A branch wire 355 leads through relay L|2 to the main power switch Si I in the control handle 452. When the gunner grasis the control handle 22 he closes switch SII grounding wires SI5 and causing the relay LI?x te close, passing current to the entire turret. Leading from relay LIE is a wire SI5 which passes through the relay box and back t the control box where it supplies power to the control box motor 430. Thus when the gunner closes switch SI I he causes current to ilow to motor itil and the cams 442 start to rotate.

Branching from wire 8l@ near the cam 442 is a wire SI1 leading to a double relay LIS. Leading from relay LI3 is a wire SIB which passes down the central column to a resistance R2. The other side of resistance R2 is connected to a wire 8I9 leading down the column out through the brushes and to armature A3 of the azimuth motor 228. Also branching from wire SI near the cams 442 is a wire 320 leading to a second double relay LI4. Leading from relay Lll is a wire B2i which leads upwardly to a resistance R3 the other side of which is connected to a wire 822 leading to armature A4 of the elevation motor 225.

Referring to Figure l2, the iields of the elevation and azimuth motors are also connected to power wire SIB. Branching upwardly from wire SI5 near the center column is a wire 823 leading to a field reverse relay LIE. Connected to one finger of relay LI5 is a wire B24 leading to a field F4 of the elevation motor 241, the other side of which is connected to a wire 825 leading to a resistance R4. A wire 826 connects the other end of resistance R4 to the other finger of relay LI5. Branching downwardly from wire SI5 near the center column is a wire 821 leading down the column and out brush box to afield reverse relay LIB for reversing the azimuth motor 223. Leading from one finger of relay LIB is a wire 828 which connects to a eld F3 of the azimuth motor 228. The other end of field F3 is connected to a resistance R5 and a wire 83!) connects the other end of resistance R5 to the other linger of relay LIS.

Referring to the control box in Figure 12 it will be noted that when the breaker arms 4M close on contact 450 that a current through the armature relays-LIS and Lili is grounded operating the relays. The ground currents consist of four branches from wire BIS, wires BSI and 832 passing through relay LIS and connected to the azimuth breaker arms MA and wires 833 and 83@ passing through relay Lili and connected to the elevation breaker arms 444. Since each cam 442 of a pair is rotated 180 with respect to the other, the general tendency is for the two contact members of relays L3 and LI4 to be alternating in breaking contact. Depending upon the position of the contacts 45B with relation to the breaker arms 444, the contact members of the relays may both be opened or closed at any one instant. If varying the position of contact 45D, the normal flow of current may be interrupted varying amounts until it is completely stopped, thus giving speed control through a large range from a few R. P. M. of the motor up to several thousand.

In addition to the speed change by varying the duration of the interruptions of current to the azimuth and elevation motors, there is a stage speed control after the shots have been made so long in duration that the current is as continuous as possible. This second stage of high speed operation is effected automatically as the gunner moves the handle A82 to an extreme position in either direction of both azimuth and elevation movement. This high speed is obtained by increasing the armature current and decreasing the neld in the azimuth and elevation motors. This is done by shunting around the armature resistances R2 and R4, and by opening normally closed shunts around eld resistances R4 and R5,

Branching from wire BIS near resistance R2 is a wire 835 leading to one contact of a relay L11. The other contact of relay LI1 is connected to a wire 336 connected to wire SIS. Thus when relay LH is energized a shunt circuit around resistance R2 is formed by wires $35 and 636. It will be noted that when relay LI 1 closes its movement opens a normally closed switch SIS one end of which is connected t0 a wire 831 passing down the column and out the brushes to connect to wire 830 near resistance R5. The other terminal of switch SI5 is connected to a wire 838 which likewise leads down the column and connects to wire 829 near resistance R5. It is thus apparent that when relay LIii is energized, not only is a shunt formed around armature resistance R2, but a normally closed shunt around field resistance R5 is opened, decreasing the eld current.

In the elevation motor wiring, branching from wire 821 near resistance R3 is a wire 839 leading to one contact of a relay LIB, the other contact of which is connected to a wire 84B leading t0 armature wire 322. When relay LIB is closed a shunt is formed around resistance R3 through wires S39 and Sfi. The movement of closing relay LIB opens a normally closed switch SI1 one terminal oi which is connected to a wire 8M leading to a wire 826 near resistance RII. The other terminal oi switch SI1 is connected to a wire 852 leading to wire 825 near resistance Ril. Energizing relay LI S therefore closes a shunt around resistance R3 and opens a normally closed shunt around resistance RG, decreasing the field current.

Referring to Figure 12, azimuth speed change relay LI1 is operated by the extreme movement of azimuth control cam 451i and elevation speed Change relay LI5 is operated by the extreme movement of elevation cam 412. It will be noted that both calm 45d and i12 have projections designating the extreme position of movement. When rotated to either extreme position the projections on azimuth cam 454 causes it to close a switch SIS one terminal of which is connected by a wire i353 to power wire 8 I 6 and the other terminal of which is connected to a wire 844 leading down the column to relay L! 1. Thus when either projection on cam 55H, corresponding to the extreme position of the cam, come into register at the top it will close switch SIB causing the speed control relay LIT to function. Although cam 465i is shown schematically in Figure 12 as a rotary cam, actually it moves axially to effect its control iunction. However, the switch unit actually used (but not shown) in place of the schematic snowing of Figure 12 is a switch having a movable member axially arranged and having two high points thereon to be contacted by the cam at either extreme of axial movement to close the switch SIB.

Elevation cam 12 operates in a manner similar to azimuth cam 554 t0 close a switch SIS. One terminal is connected to a wire 8fi5 branching from power wire SIS. The other terminal of the switch is connected to a wire BIS leading to relay LIB. Thus whenever the projections on cam 4112 register, switch SIS is closed and the elevation speed change is thus effected. Cam 1312 is shown in its actual embodiment herein in Figure l2 as a rotary cam. The exact construction however was not shown previously to keep mechanical 21 features of the control box separate from the electrical features.

The field reverse relays Ll and Lili are operated also by the elevation control cam 472 and the azimuth control cam 464 respectively. It will be noted that each cam in Figure 12 has a relieved portion on the bottom. rIhis portion represents the travel of the cam in traversing the speed range from zero to one extreme. When the cams 464 and 4l? are moved from zero to the other extreme they actuate switches S20 and SEI respectively. Switch S23 takes current from power line BIS and passes it to a wire 241 leading down the column and out the b-rushes to eld reverse relay Lit. Energizing relay Ll causes it to reverse the direction of current through azimuth eld F3 from that shown reversing the motor 223. When elevation cam 412 passes the zero or neutral position the direction away from its relieved portion it causes a switch S2! to open which takes current from. wire 816 and passes it to a wire 84S leading to field reverse relay Lib. Actuating relay Ll3 causes current to pass through field F2 in a direction opposite from that shown, thus reversing the elevation motor |46.

The operation of the simplified circuit shown in Figure 12 is as follows. Current flows from battery B2 to relay LIZ. When the gunner grasps control handle 4132 he closes switch Si l actuating relay L|2and passing current to power wire SI5 leading to azimuth relay L13 and elevation relay LII! and to control box motor 430. Motor 435i causes cams 442 to rotate rocking vbreaker' arms 444 so that they intermittently are grounded at contact 45@ causing the connected part of the relays L53 or Llll to break contact for the duration of the ground at contact 45S. The position of the contacts 450 are varied by manual control of elevation cam 41.2 and azimuth cam 464. By changing the duration of the ground at contact 450 the duration of the current interruption at relays Lit and Lili is varied, thus giving a speed control for the azimuth and elevation motors. Current passes through wire BFS connected to relay Ll3 leading down the column to resistance R3, to wire 8l!) and out the brushes to the azimuth motor, armature A3. Current passes through wire 82l leading up from relay LI4 to resistance R3 to wire i322 and to the elevation motor armature A3.

If a greater speed is desired than is obtainable at the position of the control cams when current is flowing uninterruptedly to the motor armatures, the control handle is moved to the extreme position for both azimuth and elevation in either direction, This movement causes the projections on azimuth cam 464 to close switch SIS which passes current to wire 844 energizing relay Ll?, Relay Ll'l then closes shunting current around resistance R2 and thereby increasing the armature current. The movement of relay Ll'l opens normally closed switch Sl thereby breaking a shunt around the field resistance R5, and decreasing the held current. This decrease of field current together with an increase in armature current causes azimuth motor to operate at an extremely high speed.

Likewise movement of elevation cam 412 to either extreme position causes its projection to close switch SiS. passing current to wire 845 energizinfr relay LIS which then closes to shunt out armature resistance R3 increasing armature current. The movement of relay Ll causes normally closed switch Sil to open, breaking a shunt around iield resistance R4, decreasing field 22 current. Increasing the armature current and decreasing the held current causes the armature A4 of the elevation motor 241 to rotate at a very high speed.

The reversal of the azimuth and elevation motors is also effected by manual operation of the control cams 45t and 4W. Each cam is recessed on the bottom for a space corresponding to full movement of the cam from zero to one extreme. When the cams are rotated in the other direction from the zero point they close switches controlling the field reverse relays Ll 5 and Ll E. Moving azimuth cam t', past the center point and away from the recessed portion closes switch S23 passing current to wire t4? which actuates relay LIB, reversing the field current from the direction shown. Likewise, movement of cam 412 past the center point closes switch SZl passing current to wire Bilt which actuates relay L55 reversing the field of elevation motor 24T.

The complete electrical power system is shown in Figure 13. The complete system differs from the simplified system of Figure l2 by the addition of a dynamic brake and controls to make the lower limit of elevation of the guns dependent upon the position of the guns and azimuth. The provision of a dynamic brake causes the stopping of motors by causing them to act as generators. This dynamic braking is eiective in both elevation and azimuth motors when a given limit of movement is reached, and for a short interval after the gunner releases his grasp on the control handle. The varying lower limits of the guns in elevation are provided to roughly conform the lower limit to the shape of the airplane structure in which the gun is mounted.

The parts of the circuit identified in Figure 12 are readily recognizable in Figure 13. In the wire 8l9 to the azimuth armature A3 however a relay L59 is inserted to cause the azimuth motor to act as a dynamic brake. The wire 8l9 therefore leads to dynamic brake relay Li 9 and a wire B49 leads therefrom to armature A3. In normal position relay Lia connects wire SIS to wire 849 allowing normal operation of armature A3. When relay Lig is energized, however, it grounds wire 549 allo-wing a large current to ow through wire 84d to ground thus imposing the greatest possible load cn the azimuth motor 228 when acting as a dynamic brake. The circuit for actuating dynamic brake relay L19 will later be described.

It will be noted that the movement of relay Lili actuates a switch S29 which closes during dynamic braking to shunt out resistance R5 from the azimuth held circuit. Switch SZ is connected to wire 332i which is one part of the speed change shunt and the other terminal of switch Sie is connected to a wire e connected to wire 83? the other part of the speed change shunt. Thus a shunt circuit is formed around held resistance R5 through wires 838, switch 52! and wire 859 and wire 523i which is operative during dynamic braking to produce the greatest possible held in motor 228.

Referring to Figure 13, a dynamic braking relay L28 is provided for the elevation armature circuit also. Relay L23 is connected to armature wire B22 and a wire 85! leads therefrom to elevation armature A4. Relay L2?? also operates a iield shunt switch SE2d. One terminal of switch S22@ is connected to wire 842 and the other terminal is connected to a wire 855 which connects to wire 84 i Thus when elevation brake relay L20 is actuated, the armature A4 is ground- 23 ed and the resistance R in the eld circuit is shunted. This produces the maximum load on the armature Ad and greater strength in field F4. Each cam is recessed. on the bottom for a space corresponding to full movement of the cam from zero to one extreme,

Several additions to the electrical circuit to accommodate the dynamic braises are also shown in Figure 13. 1t will be noted that the operation of power relay Liz operates three switches S22,

and Sfl. When power relay L52 is energized it closes normally open switch S22 and opens normally closed switches S23 and S24. Switch S22 is connected to a wire Sts leading to a time delay relay L which has the characterisn tic of maintaining its energizat n for a short timeafter the energizing current has been cut off. Relay- L2i is connectedy on one side to a branch from main power wire iiii and on the other side is connected to a wire E352 which is connected at the central column to the elevation held wire 823 and to the azimuth held wire EN. Thus energizing the power relay L52 closes switch S22 which energizes time delay relay L21 causingv current to iiow to the azimuth and elevation motor elds. After power relay LEZ is deenergized, delay relay Ll continues to pass current to the motor field for dynamic braking because of its time delay characteristic,

Switch S22 is connected to held supply wire 85E on one side and on the other side is connected to a wire 353 leading down the control column and out. the brush box to energize dynamic brake relay L-i 8. Switch Sid is likewise connected on one side to wire i552 and the other side is connected to a wire 85d lead" -g up the column to energize elevation dynamic brake relay LZ. Thus when power relay L52 is energized no current passes to the dynamic brake relays because switches S22 and Sie are open, but for a short time after deenergization cf the power relay LIZ (at which time switches and are closed) current passes to the dynamic brake relays because time delay relay L2# continues to pass current to wire 852.

The purpose of? the dynamic brake circuits just described is to provide a dead-man control 'for dynamic braking. If the gunner were moving the guns rapidly at the instant he was shot, there might be a possibility that the guns would travel through their normal limit control and damage the turret or the airplane. Thus the instant the gunner relaxes his grip because of injury, and the main power is cut off at power relay LIZ, the dynamic brakes are applied to stop the movement of the guns. The dynamic braking is possible only by maintaining a eld in the elevation and azimuth motors and this purpose is served by time delay relay SEE. The actual application of the dynamic brakes is by means of relays Ll and L25 operated by switches S23 and S24 respectively.

The circuits for operating the dynamic brake relays Lie and L at the limits will now be explained. It will be remembered that the only limit or moving the guns in azimuth is when the guns are near 9d" elevation and pointing toward the rear. 11 it is then desired to swing the guns clockwise or .counter-clockwise in azimuth the guns. would strike the fuselage of. the airplane in which the turret is mounted. These two positions are represented in azimuth movement by cam liil which has a notch corresponding to the counterclockwise limit and cam it which has a notch corresponding tov the clockwise limit.

'Ihese two limit cams operate in combination with elevation cam dit corresponding with the elevation position of the gun. IThe three cams operate switches in a circuit which will now be described and only when the elevation cam and an azimuth cam act together is there an application of the dynamic brakes.

Still referring to Figure 13, branching from wire 339 near the azimuth field resistance R5 is a wire 855 leading around to a switch S25 actuated by counterclockwise limit cam 484. Wire 83d is at a high potential only when the relay Llc is in the position shown in Figure 13, operating the turret in a counterclockwise direction. When the turret reaches its counterclockwise limit, cam idd closes switch S25 passing current to a wire 356 leading around to the column and up the column to elevation switch cam M4. When the guns are at a substantially horizontal position the switch cam liil will make contact passing current to a wire l which leads part way down the column until it connects with wire i353. It will be remembered that wire 853 controls the azimuth dynamic brake relay Lie.

Branching from wire 8d? near azimuth eld relay Lid is a wire 858 leading around to a switch S25 actuated by clockwise limit cam 406. Wire lill is the wire energizing neld reverse relay L55 and when energized, the turret rotates clockwise. When the turret rotates to its clockwise limit, switch S25 will close also passing current to wire tt. If switch cam @i4 is in the proper position current will ow to wire 851, thence to wire 853 and actuate the azimuth dynamic brake.

The limits of movement of the upper turret in azimuth have now been described, and the remaining limits are limits on the elevation movements of the turret. When the guns are pointing aft or toward the rear, the fuselage of the airplane will permit them to be depressed to a horizontal position. When the guns are pointing toward the front or fore position and the sides, the shape of the airplane stops them short of the horizontal position upon depression. The upper limit of elevation is the same for all positions of the turret in azimuth and is the zenith or straight upward position.

Referring to Figure 13, the upper elevation limit is regulated by azimuth cam 412. Current is supplied by tapping elevation field reverse relay wire Sli, which is energized only when the current is in a direction to cause elevation of the guns, the tap being wire 852i leading to a switch S2? actuated by the limit cam M2. When the guns are elevated to the zenith positionv the cam M2 permits switch S21 to closepassing current to a wire 85E) connected to the elevation dynamic brake wire Stil. Thus whenever the guns approach the zenith the elevation dynamic brake is applied.

The lower elevation limits for the aft position are actuated by the combination of azimuth switch cam die and elevation switch cam ME. Branching from elevation eld wire 92d is a wire Bt leading down the central column and around to azimuth switch cams 453 and 23. Field wire 826i is at a high potential only when the guns are being depressed. When the turret is pointing aft in azimuth the switch cam Sill closes and passesY current to a wire 862 leading around to the column and up the column to switch cam dit. 1f the guns should now be depressed une til they approach horizontal, the switch cam M6 willmake contact and pass current to the wire 

